Cross-contamination between patients, for example, dental patients, can occur when suctioning devices attached to vacuum lines are used to remove various bodily and/or externally introduced fluids. Although the disposable distal ends of these devices typically are changed between patients, the vacuum lines employed typically are not changed. Saliva, blood and other contaminants pass from the distal end into the vacuum line, where they can remain until arrival of the next patient. When a new distal end is inserted onto the vacuum line for a new patient, contaminants from the previous patient can backflow from the vacuum line into the distal end and enter the patient's mouth, for example. Clearly, with the growing concerns over infections like the Bird Flu and the incidence of AIDS, Hepatitis and other communicable diseases, this is a situation to be avoided.
A number of prior art devices have attempted to prevent backflow and the resulting likelihood of cross-contamination between patients. U.S. Pat. Nos. 5,425,637 and 5,509,802 to Whitehouse, et al. and U.S. Pat. No. 5,464,397 to Powers, Jr., which are incorporated herein by reference, disclose prior art attempts to prevent or at least minimize contaminant backflow and cross-contamination. The two Whitehouse patents disclose suction lines having vacuum-release apertures through a tubular sidewall of a saliva ejector tip. If a patient closes his or her lips around the tip, the vacuum-release aperture is said to prevent creation of a temporary high vacuum in the patient's mouth; the aperture also likely prevents stoppage of air and/or fluid, at least between the aperture and the rest of the system. The Powers, Jr. patent, on the other hand, appears to rely merely on a “tortuous path” within the device to substantially prevent backflow of bacteria.
However, as recent studies are believed to have shown, a boundary layer can form around the internal circumference of many currently used suctioning devices. The boundary layer is the portion of air and/or other fluid flowing in the immediate vicinity of the internal circumference. Flow at the boundary layer is severely reduced, even eliminated due to the forces of adhesion and viscosity caused by the internal circumference. Because suction within the boundary layer is reduced or eliminated, a “bio-film” can be created, allowing saliva, blood and other contaminants to flow by gravity, for example, from the main vacuum system of a dental office, through saliva ejector assemblies and into the mouths of patients.
It is not believed that prior art suctioning devices adequately account for or address backflow caused by boundary layer conditions, and/or other conditions such as mouth-induced backflow suction. Prior art devices thus allow an unacceptably high likelihood of cross-contamination between patients. Clearly, a need has arisen for a solution to this problem.